Proton and deuteron production in Au+Au reactions at<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>1</mml:mn><mml:mn>1</mml:mn><mml:mo>.</mml:mo><mml:mn>6</mml:mn><mml:mi>A</mml:mi><mml:mi> </mml:mi><mml:mi mathvariant="normal">GeV</mml:mi><mml:mo>/</mml:mo><mml:mi>c</mml:mi></mml:math>

Proton and deuteron distributions from $11.6A \mathrm{GeV}/c$ Au + Au collisions measured by the E802 Collaboration in experiment E-866 are presented. The invariant yield of protons and deuterons is studied as a function of the transverse mass for different cuts of rapidity and centrality. At low ${m}_{t}\ensuremath{-}{m}_{0}$ the proton and deuteron invariant spectra deviate from a single exponential shape. The average ${m}_{t}$ as function of centrality and rapidity is used to explore the effect of collective transverse flow in the reaction. The ratio of the deuteron to squared proton yield as a function of transverse momentum, rapidity, and centrality is used to probe the coalescence model of deuteron production. This ratio is constant as a function of rapidity only for the most central cuts and decreases with the centrality for every rapidity cut. The ratio of the differential cross section of the deuteron to the squared differential cross section of the proton, for the most central cut, is not constant as a function of ${m}_{t}\ensuremath{-}{m}_{0}.$